Generally, a PSC box bridge or a SBG bridge is a representative type of a long and large bridge whose span is long. In the case of inspecting whether or not there are cracks or corrosions on a lower surface of a bridge between a girder and another girder, a workbench or a moving path such as a scaffold is installed between a girder and another girder on the lower portion of a bridge, and then a worker observes and investigates visually whether or not there are cracks and corrosions on the lower surface of the bridge, using the workbench or the moving path.
However, the costs of visually inspecting cracks or corrosions of a bridge are expensive as described above, since a workbench or a moving path such as a scaffold should be installed. Moreover, when much wind blows, the workbench or the moving path sways, and thus there is a disadvantage safety of a worker or workers cannot be ensured.
In addition, when a bridge inspection work is visually performed, only a worker can see data of corrosions or cracks of a bridge. Accordingly, an inspection work is not reliable, and the data cannot be stored. As a result, there is a problem that a review or analysis of the inspection data becomes difficult later.
Therefore, in order to solve the above-described problem, there has been proposed that a mobile robot provided with a camera whose position control is possible passes a bridge inspection path of the lower portion of a bridge, photographs the lower portion of the bridge, processes the photographed images, and carries out appearance investigation of the bridge.
However, when the above-described mobile robot is used to move on a flange between a girder and another girder of a PSC box bridge in order to inspect the lower surface of the bridge, or to inspect the inner portion of the box of a SBG bridge, there has occurred a problem that the mobile robot cannot continuously move because of obstacles such as partitions, bridge joint members or vertical stiffeners which are provided in a box. Accordingly, when the mobile robot avoids the obstacles and moves, there has occurred a problem that a position of the bottom surface of the bridge is changed, and the bottom surface of the bridge cannot be successively photographed.
In addition, since images photographed according to position changes of the mobile robot have respectively different position information (for example, coordinates that correspond to in an altitude or distance from a camera), there are problems that a lot of errors occur in processing continuous images in correspondence to a photographing position, and accordingly reliability regarding an image analysis is lowered in the case that a defect analysis regarding a bridge is carried out.